Claroline练习追踪中只统计有成绩的学生

exercise/track_exercises.php中：

foreach( $exo_users_details as $exo_users_detail )

{
if ( $exo_users_detail['attempts'] == 0 )
{
  continue; //添加本行。
$exo_users_detail['minimum'] = '-';
$exo_users_detail['maximum'] = '-';
$displayedAverage = '-';
$displayedAvgTime = '-';
}